jon lapook has more. >> reporter: worrisome news for the more than 7 million americans who have taken chantix. a new analysis links the pill to a 72% increase in the risk of heart problems. johns hopkins dr. singh led the research. >> it is causing the same problems that we are trying to prevent, that's why it's not worth the risk. we need to prevent cardio disease among smokers, not increase. >> reporter: the review combines 14 studies involving more than 8,000 patients. while a 72% increased risk sounds alarming, the companion editorial titles, is it a heartbreaker? notes that cardiovascular problems including chest pain, heart attack and stroke are still rare. occurring in only about 1% of patients taking chantix. the drugmaker pfizer questions the way the analysis was conducted. dr. gail caldwell is vice president of medical affairs for pfizer. >> we will continue to do a more in-depth look as the fda is asking us to do but to date we have not seen evidence of important risks to the heart health of patients. from chantix. >> reporter: in mid june the fda warned chantix might be li